Cobalt(II) Chloride Hexahydrate as an Efficient and Inexpensive Catalyst for the Preparation of Biscoumarin Derivatives

Table 3

Effect of solvents in reaction of 3-nitrobenzaldehyde and 4-hydroxycoumarin catalyzed by CoCl₂·6H₂O.

Entry	Catalyst	Solvent	Time (min)	Yields (%)^a
1	CoCl2·6H2O	EtOH	4	95
2	CoCl2·6H2O	H2O	3	97
3	CoCl2·6H2O	H2O : EtOH (1 : 2)	4	96
4	CoCl2·6H2O	H2O : EtOH (2 : 1)	3	98
5	CoCl2·6H2O	H2O : EtOH (1 : 1)	2	98
6	CoCl2·6H2O	Solvent free	2 h	Trace

All reactions were catalyzed by CoCl₂·6H₂O at 70°C.
^aIsolated yields.